This thread is for questions that don't deserve their own thread.
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>give context
>describe your thought process if you're stuck
>try wolframalpha.com and stackexchange.com
>How To Ask Questions The Smart Way catb.org
>come up with a clever name for this Neanderthal
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is applied science a respected field, specifically, Forensics or is it a waste of time?
>NeandertrednaeN
I must prove that the linear operator [math]A:H^4(\mathbb{R};\mathbb{R})\to L^2(\mathbb{R};\mathbb{R}) [/math] defined by [math]u\mapsto −(1−\partial_{xx}^2)^2u [/math] generates a [math]C_0 [/math]-semigroup on [math]L^2 [/math].
I believe that we also got hinted that Fourier transforms are needed here, so I found [math]F(Au)(\omega)=F((-1+2\partial_{xx}^2-\partial_{xxxx}^4)u)(\omega)=(-1-2\omega^2-\omega^4)F(u)(\omega)
=-(\omega^2+1)^2F(u)(\omega) [/math], but I have no idea how to apply any generation theorem like Hille-Yosida or Lumer–Phillips now.
Could anybody give a verbal outline of the proof so that I can understand what should happen here?
What were the best and worst sci memes of 2017?
Best meme ever is trolley problem and worst in the red eyed guy
worst meme ever is the wotjak mini brain flood
Zenos paradox of achilles' race provided results which he ignored to instead imply infinite work sums on arbitrary numbers can produce finite results via convergence.
Zeno was smartstupid and was a paradox himself.
The way I see it, determining a black hole's size or diameter seems impossible. At any distance greater than the event horizon, light from the sides of the black body and even behind the POV gazing towards the hole would be bent and refracted back towards the POV. The POV wouldn't witness the iconic artistic impression of a black silhouette circle when the focal location of the black hole is refracting surrounding light towards the observer, but may be able to detect the warping refracting properties usually associated with those artist mock-ups. Only once the POV has passed the event horizon would such an artistic impression begin to be a possible view, but that would also imply more questions with less answers to even validate if it actually visually identifies as a "hole that is black" or if the POV would just be destroyed immediately before even being abled to acknowledge any determinable surface features, even if only a silhouette. The black hole, instead of being a hole, is more like a taughtly pinched table cloth pulled from the center of the table. The cloth, the fabric of spacetime, meets at a singular stretched area between the finger tips. Unlike the cloth though, the black hole's spacetime pinch would stretch into another dimension or even infinity, as if to cover the pinching fingers of the tablecloth with another cloth so to not be able to determine just how much tablecloth has been pulled into the pinch.
tl;dr if you see a "hole" its already too late.
Black holes have not been shown to exist in reality.
>wtf dense objects dont exist
>>wtf dense objects dont exist
Who are you quoting?
*whom
*whomst'd've'ly'yaint'nt'ed'ies's'y'es
I am using R for basic statistics and I would like to know more about the following two claims I picked up:
- The linear model regression function lm() determines an intercept and a slope. The intercept is the same as the mean of the predictor, and is the same as a regression of the predictor to a vector of all 1's.
- Regression in N variables can be reduced to a regression N-1 variables, which means regression in N variables can be reduced to repeated regression in one variable.
Can someone point me in the right direction for these questions? Google brings up a lot of stuff but most of them are tutorials which avoid these questions.
I believe that the reliability of Forensic science has been strongly questioned recently
Is there any point to finding series solutions of differential equations by hand? Am I a brainlet for using Mathematica?
You are a brainlet for trying to find solutions of differential equations in the first place.
>lm() determines an intercept and a slope
In the case of a single-term regression, yeah. But you can do things like lm(y ~ 0 + x, ...) which has no intercept term and also things like lm(y ~ 1 + x + I(x^2), ...) which returns three coefficients.
>the same as a regression of the predictor to a vector of all 1's
lm does least-squares so yeah there's a column of 1s in the matrix if you want an intercept which, as I said, is optional. A better way to think about it is as x^0.
Don't know about the second thing.
...
Is it gayer to fuck a pre-op FTM or pre-op MTF, assuming you're male?
How do you do that in Mathematica? I'm only aware of Maple having an option for series.
What?
You can use DSolve to find the solution and use Series to get an expansion. Or you can do it manually by setting y equal to a general power series and solving for the coefficients in the expansion.
Example of the latter?
I don't normally go on Veeky Forums so excuse me if this is a dumb question.
I'm interested in learning about Astronomy. Aside from le Reddit where should I go online? Does anyone here have telescopes n shit? If so spoonfeed me pls - shit like basics, gear, info etc.
Couldn't find anything about it in the catalog. Seems like a fun and interesting hobby to have.
Pretty simple, tbqhwyf.
But how do you get the [math]a_k[/math]s out of that
Is going to community college for your gen eds/introductory classes and then transferring actually a good idea? It obviously saves money, but perhaps you would be getting a subpar education that doesn't transfer over well? Maybe it would cripple you socially?
I solve for them manually, because I'm not that familiar with Mathematica and usually I only need 3-5 terms for my assignment.
For the record I think Mathematica is a much better general programming language than Maple but from what I've seen Maple's mathematics routines are more advanced than Mathematica's, particularly in the area of differential equations.
Might be worth looking into if you're taking a class on them.
If the quantum entanglement is instantaneous, why is not possible the information transmission instantaneously in quantum teleportation?
MIRETHAL IS HIS NAME, HE IS QUITE A MIRACLE!
Only reason I use Mathematica is because it's free for my university. Is Maple discounted for students? It looks pretty neat.
Is this a valid group? I'm not convinced I haven't missed something.
The set is reals excluding 0 but with an extra element I'll call "infinity". The operation is a*b = ab/(a+b), except a*inf = a and a*(-a) = inf.
Basically parallel resistors with inf for open circuits and with negative resistances.
sending information at the quantum level is inherently impossible due to uncertainty
completely retarded fucking brainlet here trying to get into math. I looked over the definitions but i don't understand the notation here at the very bottom. based on what i read earlier shouldn't the answer be everything but integers? I feel like the union symbol is being used to mean something like "skip over these numbers" or am i completely misunderstanding something? Also is this a good book?
How to think like a mathematician by Kevin Houston. Would it be better to just get the Gelfand treatment?
>based on what i read earlier shouldn't the answer be everything but integers?
That's what it says
Theoretically, what would happen if a guy came inside a woman and by some mishap she got pregnant with a dozen children? What would happen to her body as she went through pregnancy? Would her organs be crushed at some point?
The parenthesis denote open intervals. It's saying the set contains all the numbers between the integers, but not the integers themselves.
>A better way to think about it is as x^0.
I like that one. Thanks!
What is a derivative and what does it do? I'm watching 3blue1brown and I keep rewatching the vids but I don't quite get it. I understand the part where he talks about speed at a particular point for example, to be able to calculate it you must take a minuscule change into consideration and that is how you get the approximation of speed at a particular point in time. If you only had information about 1 point in time and 1 point in space/distance, you could only get an average where you don't know at what point the card sped up or whatever.
But what is a derivative?
Just think of it geometrically. It's the slope of the tangent line at a point. This generalizes much more nicely than velocity in higher dimensions.
Yeah, but what does it represent? Like, I get it because you get ex. v=ds/dt so yeah, velocity is the result, velocity is the derivative in this sense, right? We derived velocity from a distance vs time graph, but what is the formula were x=a*b, and we're trying to derive x? Then we can't use a vs b graph, since there would be no rise over run? I hope you get what I mean.
>I hope you get what I mean.
I don't, sorry. Draw a picture?
do imaginary angles exist?
They do if you define them.
Because you have no way of killing the cat before opening the box, and no way of telling if the other fucker opened his. You just know that if/when he opens the other box, his cat will be in the same state as yours.
Nevermind, I spent some more time with it and it's isomorphic with (R, +, 0) with x -> 1/x, inf -> 0
Got my first Anthropology class in about an hour, what should I expect?
Sine and cosine can be defined for complex inputs through their Taylor series.
I suppose you could try to come up with a geometric interpretation of that.
>anthropology
lol
Rather than Taylor series, just use complex exponentials. Really it's the best definition of sine and cosine anyways.
en.wikipedia.org
>antropology
poor bastard...
I am trying to do the following problem:
Let [math] P(x) [/math] be the 2015th degree polynomial such that [math] P(x) = \frac{1}{x^2} [/math] for all [math] x =1,2,...,2016 [/math]. Find [math] 2017P(2017) [/math]
I feel like I do not know the technique that I'm supposed to use. But let me show my current work:
The 2017th degre polynomial [math] x^2 P(x) [/math] will be equal to 1 for x=1,2,...,2016. And then the polynomial [math] x^2 P(x) - 1 [/math] will have a root at x=1,2,...,2016. This means I may write:
[math] x^2P(x) - 1 = (x-1)(x-2)...(x-2016)Q(x) [/math] where, necessarily, [math] Q(x) = ax + b [/math] (it must be linear).
Now, let's evaluate this expression for [math] x=0 [/math]. We get that [math] -1 = (2016)!Q(0) [/math] and thus [math] Q(0) = \frac{-1}{2016!} [/math] which implies [math] b = \frac{-1}{2016!} [/math].
This means the only unknown left is a.
Also, by evaluating that expression for x=2017 I found that [math] 2017P(2017) = (2016)! a [/math] which means the problem is equivalent to computing a. Any ideas?
notice x^2 P(x) - 1 has no term of order 1
chicks
Damn man you are a genius. I haven't done it yet but I see how that can compute a. I will report back when I get it.
Trying to port the code in this stats textbook from R to Mathematica. Here he's doing OLS with increasing order. I've got the fit lines but I can't figure out how to get the bounds.
Copied
github.com
for the first order regression but it doesn't seem to work for higher orders.
I got it my man. Thank you.
Am I retarded or what? I am trying to wrap my head around the instantaneous rate of change at a certain point, but here's the problem. I understand that rate of change helps me compare two pairs of points, where both have their own rate of change, so when I compare both rates of change I can see for example that for points a and b on x axis I reached less of y that between points c and d, where I reached more y. If that makes sense. And this clicks when thinking about speed. Cool, I can get exact speed at a point using diff. calculus. But when thinking about it in any other way, what the fuck does rate of change at a single point even mean? I probably even got the former wrong, the more I try to educate myself on this the less I seem to understand and just get more confused the more I read... I'm a fucking brainlet...
It's the slope of the tangent line at that point.
Why x and y axes form a 90° angle? I understand that it makes sense, but why does it make sense?
...
cos(ix)=cosh(x)
sin(ix)=i*sinh(x)
why does 1+1 equal two and not eleven?
360 degrees is defined to be 1 rotation. So if you have 4 quadrants you get 4 angles of 360/4 = 90 degrees.
I want to go into Gene Therapy. What should I major in? I'm currently going to dual major biophysics and biochemistry
nice and original, never post again
because of linear algebra.
basically bc if two arrows point at not a 90 deg angle, then the will have some component arrow that points in the same direction as the other line.
I think its related to span, but i could be remembering wrong
youtube.com
...
It depends on what you define by "angle".
If you mean the arguments cos (or some other trigonometric function) can take, then sure, any complex number can be interpreted as an angle.
>But when thinking about it in any other way
Like, what kind of way?
anyone interested in Astronomy? Where do I go?
Star maps, NASA, read about it
Just like you research anything else
ok cheers brah. I figured as much, I was really just wondering if there are any neat resources I should be aware of.
Sky news magazine is what got me interested, astrophotography is pretty neat
but there are definitely real time star maps online, and I think something called google sky exists
>23
>haven't done real math since highschool
>remember loving the subject so i decide to brush up on khan academy
>having issues with simplifying square roots with variables
is this normal
Thanks again man.
>real time star maps online
Yeah I found the program 'Stellarium' which is really good. So far I've just been fiddling around with it.
>man
I'm not a "man".
If you never really learned math properly in the first place, like many schools unfortunately, then yeah it can be hard to get back into. But the important part here is that you're getting back into it. Hopefully now that you're older you won't be afraid to ask questions and will take your own time outside the"classroom" to learn and find help.
>real math since highschool
Highschools don't do real math though.
>Highschools don't do real math though.
Which high school for brainlets do you go to?
I saw a cat sit on a wall for a while, not 30 minutes later a storm passed over the wind howling in the night.
Did the cat know it was coming?
And if it did, how?
It's a statement about every single highschool.
>It's a statement about every single highschool.
You mean "a false statement".
Since when do high schools teach algebraic geometry, homotopy theory and so on?
>homotopy theory
>real math
pick one
can two planet co exist in the same orbit? assuming that they are carbon copy of each other (same mass, speed, gravitational force etc)
if it is possible then how so? would it be like the example maintaining the same distance since they have the same speed without colliding with each other in the near future or the bottom example where both form their own mini orbit in a constant state of push and pull while orbiting around the sun?
i am a brainlet and this question is burning me for a while. please help
Animals have better senses, so things like temperature and atmosphere pressure change that humans need tools to measure, animals can already sense it.
>Since when do high schools teach algebraic geometry, homotopy theory and so on?
Since when are those "real math"?
>the red eyed guy
[picture needed]
Now I see you simply have no idea what you're talking about, stay in your lane next time you're this uninformed about the topic at hand.
Trojan asteroids yo
That's what I thought.
Does the cat consciously know the storm is coming or does it decide what to do instinctively?
i guess you partially answered my question so i am thankful. however, is the bottom scenario plausible?
DUDE YOU GUYS DUDES
I spontaneously realized that
[eqn]\sum\limits_{-\infty}^{n} 2^k =2^{n+1}[/eqn]
Moreover, testing suggests that 2 is the least integer for which the sum converges. Replacing 2 with greater integers gives predictable forms, but the one just stated is especially pleasing to me, as the "doubling" effect rolls the base back into-itself in a way that doesn't appear to work for the rest.
What are some interesting number-theoretic notions along these lines? I know that it goes straight to series in calc so no need to mention that.
t. re-discovers babby calc shit while bored
>studying cohomology is not real math
Which spectrum are you on, by any chance?
Are you utterly thoughtless?
Am I wrong to say that those topics are not studied at high school? If so, please show me a single high school which actually teaches them.
>[math]−\infty[/math]
Not well-defined.
If I make an analogy between a computer and the universe by saying that both are made up of the same basic components (hardware/matter; software/consciusness; electricity/energy), do I sound like a total brainlet or does it make sense in some way?